Prior to the present invention, various procedures were used to cure epoxy resins. For example, Crivello, U.S. Pat. No. 4,058,401 shows that epoxy resins can be cured by use of a photoinitiator, such as a triarylsulfonium salt in combination with exposure to actinic irradiation, such as ultraviolet light. Methods for effecting the cure of epoxy resins by heat are shown by Crivello, U.S. Pat. No. 4,216,288, directed to heat curable cationically polymerizable organic materials using an aromatic onium salt initiator, such as an aromatic sulfonium salt and a reducing agent, such as thiophenol. Additional procedures for effecting the cure of epoxy resins which do not require the use of arylsulfonium salts and which impart improved toughness to the resulting cured epoxy resin is by the use of organic anhydrides for functionalized organosiloxanes, as shown by Moshinskii et al, U.S.S.R. Pat. No. 244616 (1969) [Chemical Abstracts 72 32777m (1970)]. However, the use of functionalized siloxanes as reported by Moshinskii et al suffer from the fact that the method of preparing the silicone curing agent is uneconomic, or the resulting cured epoxy resin is not stable enough for certain high temperature applications.
The present invention is based on the discovery that heat curable epoxy resin compositions can be made having improved heat distortion temperature at elevated temperatures and improved oxidative stability as well as providing elastomeric organopolysiloxanes having improved toughness by utilizing as a curing agent for the epoxy resin an effective amount of an organopolysiloxane having attached to silicon by carbon-silicon linkages at least one group of the formula, ##STR1## and thereafter heating the resulting blend at a temperature in the range of between about 50.degree. C. to 300.degree. C., where R-R.sup.5 are members selected from hydrogen, halogen, C.sub.(1-13) monovalent hydrocarbon radicals and substituted C.sub.(1-13) monovalent hydrocarbon radicals, Z is selected from --O-- and C--(R).sub.2 and Y is a member selected from --O-- and ##STR2## R.sup.6 is a divalent C.sub.(1-13) hydrocarbon radical or substituted hydrocarbon radical and X is a monovalent amine radical.